Patent Application
20160373253
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2015-123024, filed on Jun. 18, 2015; the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to a communication device, a communication system, a communication method, and a computer program product.
A quantum key distribution system is configured with a transmitter, a receiver, and an optical fiber link that connects the transmitter and the receiver. The transmitter transmits a string of single photons to the receiver via the optical fiber link (a quantum communication channel). After that, the transmitter and the receiver exchange control information with each other, and share cryptographic keys. This technology is implemented using the technology generally referred to as quantum key distribution (QKD). The cryptographic keys shared by the transmitter and the receiver are used and consumed in performing cryptographic data communication between the transmitter and the receiver or between an application connected to the transmitter and an application connected to the receiver.
In the quantum key distribution, it is important to see to it that transmission and reception of photon strings using the optical fiber link is done without any errors. However, due to the changes occurring in the optical fiber length because of the changes in the ambient temperature or due to the variation occurring in the communication characteristics such as the oscillation of the optical fiber; the state of the photons undergoes changes, and the suitable reception timing or the suitable reception light intensity undergoes variation. Such a phenomenon appears in the form of the error rate of the photon strings (i.e., the quantum bit error rate (QBER)) (hereinafter, simply referred to as “error rate”). Moreover, in the quantum key distribution, the photons used for the purpose of sharing cryptographic keys possess quantum uncertainty which is one of the basic principles of quantum mechanics indicating that the photons undergo physical changes when tapped. Due to such a principle, if the photons including the information of a cryptographic key transmitted from a transmitter are tapped (wiretapped) in the quantum communication channel by a wiretapper, then the photons undergo physical changes and the error rate goes up due to the wiretapping too. Because of such variation in the error rate, the receiver that receives the photons becomes able to detect that the photons are likely to have been wiretapped by a wiretapper. Regarding the information based on a photon string that is transmitted from the transmitter to the receiver using quantum key distribution, with the aim of cancelling out the bits in which an error has occurred due to wiretapping, a key distillation operation is performed that is accompanied by the exchange of control information as described above. The key distillation operation ensures that safe cryptographic keys are shared. However, since the number of cancelled-out bits increases in proportion to the greater error rate, the eventually-obtained cryptographic key becomes smaller in size. Herein, the amount of generation per unit of time of the shared cryptographic keys is called a secure key rate and serves as the indicator of the operation speed performance of the quantum key distribution system. That is, being able to use a number of cryptographic keys enables achieving high-speed and safe cryptographic data communication. Hence, it can be said that, higher the secure key rate, the higher is the level of sophistication of the quantum key distribution system.
The cryptographic keys shared between a transmitter and a receiver are consumed for the purpose of data encryption and data decryption during cryptographic data communication. Herein, a cryptographic communication method that is generally called the one-time pad (OTP) method is used. In the cryptographic communication using a cryptographic key according to the one-time pad method, it is ensured according to the information theory that no wiretapper having whatever knowledge can decipher the cryptographic communication. However, in the one-time pad method, since a different cryptographic key is used at the time of transmitting each piece of data, it becomes necessary to have a large number of cryptographic keys.
As far as achieving high-speed and large-capacity data communication, the present situation is that the secure key rate in the QKD is slow. In optical fiber transmission, the speed of data communication is in the order of gigabytes per second. In contrast, for example, the present situation is that the secure key rate in the QKD is in the order or megabytes. Hence, in order to use the cryptographic keys, which are shared in advance, according to the one-time pad method for the entire data, either the speed of data communication needs to be reduced or a large number cryptographic keys need to be communicated and stored in advance. However, if the speed of data communication exceeds the secure key rate, then the stored cryptographic keys are increasingly consumed thereby leading to the exhaustion of the cryptographic keys.
According to an embodiment, a communication device includes a first determining unit, a second determining unit, a first obtaining unit, a recognizing unit, and an encrypting unit. The first determining unit determines a period of time during which there is a possibility of wiretapping of data present in a data communication channel which establishes connection to another communication device. The second determining unit determines, with a length of the period of time as unit of time, size of a cryptographic key which is used for encrypting data to be transmitted to the other communication device via the data communication channel during each unit of time. The first obtaining unit obtains a first cryptographic key, which has the size, from a first storing unit which stores therein cryptographic keys that have been shared with the other communication device. The recognizing unit recognizes a possibility of wiretapping with respect to the data communication channel. Until the possibility of the wiretapping is recognized by the recognizing unit, the encrypting unit repeatedly encrypts data, which is to be transmitted to the other communication device, during each unit of time using the first cryptographic key obtained by the first obtaining unit.
Exemplary embodiments are described below in detail with reference to the accompanying drawings. Herein, the drawings are only schematic in nature, and the specific configuration should be determined by taking into account the explanation given below.
As illustrated in
The node 1 is a transmitter that transmits, to the node 2 via the optical fiber link 3, a photon string that is made of single photons which are generated by the laser and which serve as the basis for generating cryptographic keys. The node 1 performs a key distillation operation (described later) (i.e., a sifting operation, an error correction operation, and a privacy amplification operation) based on the photon string that is transmitted, so as to generate a cryptographic key. Moreover, during the key distillation operation, the node 1 exchanges control information (not the single photons but general-purpose digital data) with the node 2. Herein, the control information can be transferred between the nodes 1 and 2 either via the optical fiber link 3 or using another communication channel (such as the commonly-used Internet line). The communication channel meant for digital data and used in exchanging control information is sometimes called a classical communication channel.
The node 2 is a receiver that receives, from the node 1 via the optical fiber link 3, the photon string made of single photons that serve as the basis for generating cryptographic keys. The node 2 performs a key distillation operation (described later) (i.e., a sifting operation, an error correction operation, and a privacy amplification operation) based on the photon string that is received, so as to generate a cryptographic key that is identical to the cryptographic key generated by the node 1. Moreover, during the key distillation operation, the node 2 exchanges control information with the node 1.
The optical fiber link 3 is an optical fiber in which a photon communication channel is formed for the purpose of transmission and reception of photons and an optical data communication channel is formed for the purpose of optical data communication by implementing the wavelength division multiplex (WDM) technology in which light of different wavelengths is used. Herein, the technology that enables transmission and reception of photons for the purpose of quantum key distribution and enables optical data communication at the same time using the single optical fiber is termed as a “coexistence technology”. Thus, in the coexistence technology, a photon communication channel and an optical data communication channel are formed in the single optical fiber. As a result, it becomes possible to reduce the cost of laying a new optical fiber required to implement the communication system 100 representing a quantum key distribution system. Moreover, generally, the light used in the optical data communication channel has a strong optical intensity, while the light used in the photon communication channel has a weak optical intensity. For that reason, the light used in the optical data communication channel causes a noise for the photons in the photon communication channel. Because of such noise, the error rate in the photon communication channel goes on increasing, thereby making the operations of the quantum key distribution system unstable. In the coexistence technology, as a result of implementing the WDM technology, in which light of different wavelengths is used, along with a frequency filtering technology for the purpose of eliminating mutual interference in the light; it becomes possible to reduce the ratio by which the light in the optical data communication channel causes a noise in the photon communication channel, thereby enabling implementation of both channels at the same time.
The single photons output by the node 1 are transmitted to the node 2 via the photon communication channel serving as the quantum communication channel. On the other hand, communication data such as the control information is communicated between the nodes 1 and 2 via the optical data communication channel serving as the classical communication channel.
In the communication system 100 including the nodes 1 and 2, in case a wiretapper attempts to tap communication data from the optical data communication channel of the optical fiber link 3; the photons present in the optical communication channel, which is formed in the same optical fiber link 3, undergo physical changes. That leads to an increase in the error rate of the photon string, thereby enabling recognition of the possibility that the communication data in the optical data communication channel is being wiretapped.
Meanwhile, with reference to
Meanwhile, in the communication system 100, during the key distillation operation that needs to be performed for the purpose of sharing cryptographic keys between the nodes 1 and 2, the necessary control information either can be exchanged using the optical data communication channel as described above or can be exchanged using a dedicated channel implemented in the same optical fiber link 3 in which the photon communication channel and the optical data communication channel are implemented.
The data communicated using the optical data communication channel can be any type of data. As described earlier, the control information required in the key distillation operation can be exchanged as data or some other general-purpose data can be exchanged using the optical data communication channel. For example, consider a case in which the communication system 100 is built and implemented as part of an optical data communication infrastructure. It is possible to think of a possibility in which the node 1 or the node 2 is equipped not only with the function of sharing cryptographic keys but also with the function of an optical transceiver so as to enable an external device to communicate data via the optical fiber link 3. In that case, the data communicated by the node 1 or the node 2 using the optical data communication channel can be assumed to be a variety of data not limited to the communication system 100 representing a quantum key distribution system.
As illustrated in
The CPU 80 is a processor that controls the operations of the entire node 1. The ROM 81 is a nonvolatile memory device used in storing computer programs executed by the CPU 80 to control various functions. The RAM 82 is a volatile memory device that functions as the work memory of the CPU 80.
The communication I/F 83 is an interface for communicating data with an external device via a network such as a local area network (LAN) or via a wireless network.
The auxiliary memory device 84 is a nonvolatile memory device used to store various computer programs executed by the CPU 80 and to store cryptographic keys generated as a result of performing a cryptographic key generation operation. The auxiliary memory device 84 is a memory device such as a hard disk drive (HDD), a solid state drive (SSD), a flash memory, or an optical disk in which information can be stored in an electrical, magnetic, or optical manner.
The optical processing device 85 is an optical device that transmits and receives photon strings via the photon communication channel (the quantum communication channel) of the optical fiber link 3. For example, the optical processing device 85 of the node 1 transmits, to the optical processing device 85 of the node 2 via the photon communication channel, a photon string that is made of single photons, which are generated to be in a polarization state or a phase state based on base information generated using a randomly-selected base, based on a bit string (a photon bit string) that represents bit information generated using random numbers. In the photon string generated by the optical processing device 85 of the node 1, each photon holds 1-bit information of either “0” or “1”. The optical processing device 85 of the node 2 receives the photon string from the optical processing device 85 of the node 1 via the photon communication channel, and obtains a photon bit string representing the bit information by reading the received photon string based on base information generated using a randomly-selected base. Moreover, via the optical data communication channel of the optical fiber link 3, the optical processing device 85 converts data into optical signals and sends the optical signals, or converts the received optical signals into data.
Meanwhile, the CPU 80, the ROM 81, the RAM 82, the communication I/F 83, the auxiliary memory device 84, and the optical processing device 85 are connected to each other in a communicable manner by a bus 86 such as an address bus and a data bus.
As illustrated in
The quantum transmitting unit 101 is a functional unit that transmits, to a quantum receiving unit 201 of the node 2 via the photon communication channel, a photon string that is made of single photons, which are generated to be in a polarization state or a phase state based on base information generated using a randomly-selected base, based on a bit string (a photon bit string) that represents bit information generated using random numbers. The quantum transmitting unit 101 temporarily stores the generated photon bit string in the storing unit 103. The quantum transmitting unit 101 is implemented by the optical processing device 85 illustrated in
The generating unit 102 is a functional unit that generates a cryptographic key, which is to be used in encrypting the data transmitted from the data transmitting unit 106, by obtaining a cryptographic key having the length (a size L′) that is determined by the determining unit 110 in the manner described later. At that time, the cryptographic keys stored in the storing unit 103 are consumed by an amount equivalent to the size obtained by the generating unit 102. Moreover, the generating unit 102 sends information about the size L′, which represents the length of cryptographic keys as determined by the determining unit 110, to a generating unit 202 via the optical data communication channel. Meanwhile, the generating unit 102 includes a key distilling unit 1021 (a key distilling unit).
The key distilling unit 1021 is a functional unit that communicates control information with a key distilling unit 2021 (described later) of the node 2 via the optical data communication channel, and performs a key distillation operation for generating a cryptographic key from the photon bit string. The detailed explanation of the key distillation operation is given later.
The storing unit 103 is a functional unit that stores therein the following: the photon bit string generated by the quantum transmitting unit 101; the intermediate data generated during the key distillation operation performed by the key distilling unit 1021; and the cryptographic key that is eventually generated. The storing unit 103 is implemented by the auxiliary memory device 84 illustrated in
The data generating unit 104 is an application that runs in the node 1 and that handles various types of data, and is a functional unit that sends data, which is to be transmitted to the node 2 (hereinafter, sometimes termed as “application data”), to the encrypting unit 105.
The encrypting unit 105 is a functional unit that obtains the cryptographic key from the generating unit 102 upon receiving the application data from the data generating unit 104 and that encrypts the application data using the cryptographic key. Then, the encrypting unit 105 sends the encrypted application data (hereinafter, sometimes termed as “cryptographic data”) to the data transmitting unit 106.
The data transmitting unit 106 is a functional unit that converts the cryptographic data, which is received from the encrypting unit 105, into optical signals and that transmits the optical signals of the cryptographic data to a data receiving unit 206 of the node 2 via the optical data communication channel of the optical fiber link 3. The data transmitting unit 106 is implemented by the optical processing device 85 illustrated in
The wiretapping recognizing unit 107 is, as described later, a functional unit that receives a wiretapping detection signal from the wiretapping notification receiving unit 108, so as to recognize the risk of wiretapping in the optical data communication channel of the optical fiber link 3. Upon recognizing the risk of wiretapping, the wiretapping recognizing unit 107 instructs the wiretapping countering unit 109 to perform a wiretapping countering operation.
The wiretapping notification receiving unit 108 is, as described later, a functional unit that receives a wiretapping detection notification signal from a wiretapping notification transmitting unit 208 of the node 2 via the classical communication channel (such as the optical data communication channel) and that sends a wiretapping detection signal to the wiretapping recognizing unit 107. In the case of receiving a wiretapping detection notification signal via the optical data communication channel, the wiretapping notification receiving unit 108 is implemented by the optical processing device 85 illustrated in
The wiretapping countering unit 109 is a functional unit that receives an instruction to perform a wiretapping countering operation from the wiretapping recognizing unit 107 and that performs a wiretapping countering operation. The specific details of the wiretapping countering operation are given later.
The determining unit 110 is a functional unit that determines the size L′ greater than the size L of the application data sent by the data generating unit 104 to the encrypting unit 105 during a wiretapping period T that includes the time slot within which the data that is at risk of being actually wiretapped is transmitted using the optical data communication channel. Regarding the method of determining the size L′, the explanation is given later. The determining unit 110 includes a wiretapping period determining unit 1101 (a first determining unit) and a generation rate determining unit 1102.
The wiretapping period determining unit 1101 is a functional unit that determines the wiretapping period T that includes the time slot within which the data is at risk of actually being wiretapped is transmitted using the optical data communication channel. Regarding the method of determining the wiretapping period T, the explanation is given later.
The generation rate determining unit 1102 is a functional unit that determines a generation rate R′ greater than the maximum value of a generation rate R at which the data generating unit 104 generates application data per unit of time and sends it to the encrypting unit 105. Regarding the method of generating the generation rate R′, the explanation is given later.
Meanwhile, the generating unit 102, the data generating unit 104, the encrypting unit 105, the wiretapping recognizing unit 107, the wiretapping countering unit 109, and the determining unit 110 are implemented when the CPU 80 illustrated in
Meanwhile, the quantum transmitting unit 101, the generating unit 102, the storing unit 103, the data generating unit 104, the encrypting unit 105, the data transmitting unit 106, the wiretapping recognizing unit 107, the wiretapping notification receiving unit 108, the wiretapping countering unit 109, and the determining unit 110 illustrated in
As illustrated in
The quantum receiving unit 201 is a functional unit that receives, from the quantum transmitting unit 101 of the node 1 via the photon communication channel, a photon string and that obtains a photon bit string representing the bit information by reading the received photon string based on base information generated using a randomly-selected base. Then, the quantum receiving unit 201 temporarily stores the generated photon bit string in the storing unit 203. The quantum receiving unit 201 is implemented by the optical processing device 85 illustrated in
The generating unit 202 is a functional unit that receives information about the length (the size L′) of the cryptographic key via the optical data communication channel from the generating unit 102 and that generates a cryptographic key, which is to be used in decrypting the data received by the data receiving unit 206, by obtaining a cryptographic key having the size L′ from the storing unit 203. At that time, the cryptographic keys stored in the storing unit 203 are consumed by an amount equivalent to the size obtained by the generating unit 202. Herein, the generating unit 202 includes a key distilling unit 2021.
The key distilling unit 2021 is a functional unit that communicates control information with the key distilling unit 1021 of the node 1 via the optical data communication channel, so as to perform a key distillation operation for generating a cryptographic key from the photon bit string.
The storing unit 203 is a functional unit that stores therein the following: the photon bit string generated by the quantum receiving unit 201; intermediate data generated during the key distillation operation performed by the key distilling unit 2021; and the cryptographic key that is eventually generated. The storing unit 203 is implemented by the auxiliary memory device 84 illustrated in
The data using unit 204 is an application running in the node 2 for handling a variety of data and is a functional unit that receives application data that was received by the decrypting unit 205 from the node 1 and that makes use of the application data.
The decrypting unit 205 is, as described later, a functional unit that receives cryptographic data from the data receiving unit 206, that obtains the cryptographic key from the generating unit 202, and that decrypts the cryptographic data using the cryptographic key. Moreover, the decrypting unit 205 sends application data, which is obtained by decrypting the cryptographic data, to the data using unit 204.
The data receiving unit 206 is a functional unit that converts optical signals, which are received from the data transmitting unit 106 via the optical data communication channel, into cryptographic data and sends it to the decrypting unit 205. The data receiving unit 206 is implemented by the optical processing device 85 illustrated in
The wiretapping detecting unit 207 is a functional unit that obtains the error rate of the photon communication channel (the quantum communication channel) as calculated during the key distillation operation performed by the key distilling unit 2021 of the generating unit 202, that performs a wiretapping determination operation (described later) based on the error rate, and that detects the possibility of wiretapping by a wiretapper. For example, when the obtained error rate is greater than a predetermined threshold value, the wiretapping detecting unit 207 detects that there is a possibility of wiretapping. When the possibility of wiretapping is detected, the wiretapping detecting unit 207 sends a wiretapping detection signal to the wiretapping notification transmitting unit 208. Thus, herein, the data (such as application data) communicated using the optical data communication channel is the target for wiretapping intended by the wiretapper; and the possibility of wiretapping with respect to the data in the optical data communication channel is detected based on the error rate of the photon string in the optical photon communication channel that is implemented in the same optical fiber link 3 as a result of implementing the coexistence technology.
The wiretapping notification transmitting unit 208 is a functional unit that receives the wiretapping detection signal from the wiretapping detecting unit 207 and that transmits a wiretapping detection notification signal to the wiretapping notification receiving unit 108 of the node 1 via the classical communication channel (such as the optical data communication channel). That is, by transmitting a wiretapping detection notification signal to the node 1, the wiretapping notification transmitting unit 208 notifies the node 1 about the detection of a possibility of wiretapping of the data in the optical data communication channel. In the case of transmitting the wiretapping detection notification signal via the optical data communication channel, the wiretapping notification transmitting unit 208 is implemented by the optical processing device 85 illustrated in
Meanwhile, the generating unit 202, the data using unit 204, the decrypting unit 205, and the wiretapping detecting unit 207 are implemented when the CPU 80 illustrated in
Meanwhile, the quantum receiving unit 201, the generating unit 202, the storing unit 203, the data using unit 204, the decrypting unit 205, the data receiving unit 206, the wiretapping detecting unit 207, and the wiretapping notification transmitting unit 208 illustrated in
Step S11
The quantum transmitting unit 101 transmits, to the quantum receiving unit 201 of the node 2 via the photon communication channel, a photon string that is made of single photons, which are generated to be in a polarization state or a phase state based on base information generated using a randomly-selected base, based on a photon bit string (a bit string) that represents bit information generated using random numbers. Then, the quantum transmitting unit 101 sends the base information and the photon bit string to the key distilling unit 1021 of the generating unit 102.
Step S12
The quantum receiving unit 201 receives, from the quantum transmitting unit 101 of the node 1 via the photon communication channel, a photon string and obtains a photon bit string (bit string) representing the bit information by reading the received photon string based on base information generated using a randomly-selected base. Then, the quantum receiving unit 201 sends the base information and the photon bit string to the key distilling unit 2021 of the generating unit 202.
Step S13
The key distilling unit 1021 receives the base information, which is generated by the quantum receiving unit 201 of the node 2, from the key distilling unit 2021 of the node 2 via the classical communication channel (such as the optical data communication channel); and performs a sifting operation that includes comparing the received base information with the base information generated by the quantum transmitting unit 101, extracting the bits corresponding to the matching portion from the photon bit string, and generating a shared bit string.
Step S14
The key distilling unit 2021 receives the base information, which is generated by the quantum transmitting unit 101 of the node 1, from the key distilling unit 1021 of the node 1 via the classical communication channel (such as the optical data communication channel); and performs a sifting operation that includes comparing the received base information with the base information generated by the quantum receiving unit 201, extracting the bits corresponding to the matching portion from the photon bit string, and generating a shared bit string.
Step S15
The key distilling unit 1021 performs an error correction operation that includes exchanging control information (error correction (EC) information) with the key distilling unit 2021 of the node 2 via the classical data communication channel (such as the optical data communication channel); correcting the bit errors in the shared bit string; and generating a post-correction bit string.
Step S16
The key distilling unit 2021 performs an error correction operation that includes exchanging control information (error correction (EC) information) with the key distilling unit 1021 of the node 1 via the classical data communication channel (such as the optical data communication channel); correcting the bit errors in the shared bit string; and generating a post-correction bit string. Moreover, when the error correction operation is performed with respect to the shared bit string thereby resulting in the generation of a post-correction bit string, the key distilling unit 2021 calculates an error rate that represents the percentage of error bits calculated during the error correction from the number of corrected errors in the shared bits between the nodes 1 and 2. Then, the key distilling unit 2021 sends the calculated error rate to the wiretapping detecting unit 207.
Step S17
The key distilling unit 1021 receives control information (privacy amplification (PA) information) from the key distilling unit 2021 of the node 2 via the classical communication channel (such as the optical data communication channel); and, based on the PA information, performs a key compression operation (a privacy amplification operation) with respect to the post-correction bit string with the aim of cancelling out, from the EC information communicated during the error correction operation, the volume of information that is likely to have been tapped by a wiretapper, and generates a cryptographic key. Then, the key distilling unit 1021 stores the generated cryptographic key in the storing unit 103.
Step S18
The key distilling unit 2021 generates control information (PA information) and transmits it to the key distilling unit 1021 of the node 1 via the classical communication channel (such as the optical data communication channel); and, based on the PA information, performs a key compression operation (a privacy amplification operation) with respect to the post-correction bit string with the aim of cancelling out, from the EC information communicated during the error correction operation, the volume of information that is likely to have been tapped by a wiretapper, and generates a cryptographic key. Then, the key distilling unit 2021 stores the generated cryptographic key in the storing unit 203.
As a result of performing the operations described above, identical cryptographic keys are generated in the nodes 1 and 2. By performing the operations described above in a repeated manner, different cryptographic keys are generated in a repeated manner. The cryptographic keys that are generated in a repeated manner are stored in the storing units 103 and 203, and are used in the data communication performed between the nodes 1 and 2 via the optical data communication channel or are used in the data communication performed between external applications, which are connected to the nodes 1 and 2, via an external network.
Meanwhile, as described earlier, communication of base information and communication of a variety of control information between the nodes 1 and 2 during the key distillation operation can be done using the optical data communication channel. However, since the communication includes special communication closed within the quantum key distribution system and includes fundamental communication directly linked to the key distillation operation, and since the key distillation operation requires complex calculations; it is alternatively possible to form a dedicated channel in the optical fiber link 3 for such communication. In that case, the dedicated channel serves as a special channel used internally by the nodes 1 and 2 of the quantum key distribution system. Hence, the light intensity of the dedicated channel can be designed freely. If the light intensity of the dedicated channel is set to be sufficiently weak, then the noise effect produced by the dedicated channel on the photon communication channel is nearly ignorable.
On the time axis illustrated in
The wiretapping detecting unit 207 performs the wiretapping determination operation for a predetermined period of time (a wiretapping determination operation period T2 illustrated in
Herein, it is assumed that wiretapping with respect to the optical data communication channel of the optical fiber link 3 is started by a wiretapper between the timings ta and tc, that is, started by a wiretapper at a timing tb of the error rate measurement period TQ2. After the timing tb at which the wiretapping is started, there is an increase in the error rate of the photon communication channel. During the wiretapping determination operation performed after the elapse of the error rate determination period TQ1, since wiretapping has not yet started, the wiretapping detecting unit 207 determines that there is no possibility of wiretapping because the error rate is smaller than a predetermined threshold value. On the other hand, when wiretapping is started at the timing tb, during the wiretapping determination operation after the elapse of the error rate measurement period TQ2, the error rate exceeds the predetermined threshold value due to the effect of wiretapping and the wiretapping detecting unit 207 determines that there is possibility of wiretapping. Thus, as a result of performing the wiretapping determination operation after the elapse of the error rate measurement period TQ2, the wiretapping detecting unit 207 detects the possibility that wiretapping was started at some timing during the error rate measurement period TQ2 after the timing ta.
Meanwhile, if the error rate measurement period T1 is shortened, then the time interval between the timing at which the error rate measurement period started (in the example illustrated in
Alternatively, the wiretapping detecting unit 207 can determine the presence or absence of the possibility of wiretapping based on the wiretapping rate calculated by the key distilling unit 2021 at each instance of performing the key distillation operation. Still alternatively, the wiretapping detecting unit 207 can determine the presence or absence of the possibility of wiretapping based on the average value or the value of integral of the error rate during each instance of the error rate measurement period T1 or based on the moving average value of the error rate across the error rate measurement periods T1.
With reference to
As illustrated in
Once the possibility of wiretapping is recognized as a result of receiving the wiretapping detection signal, the wiretapping recognizing unit 107 instructs the wiretapping countering unit 109 to perform a wiretapping countering operation. Upon receiving the instruction to perform a wiretapping countering operation from the wiretapping recognizing unit 107, the wiretapping countering unit 109 performs the wiretapping countering operation. As illustrated in
The wiretapping period determining unit 1101 of the determining unit 110 adds the error rate measurement period T1 set as a predetermined period of time, the wiretapping determination operation period T2 set as an estimate value, the wiretapping notification period T3 set as an estimate value, and the wiretapping countering period T4 set as an estimate value; and determines the wiretapping period T (=T1+T2+T3+T4). As illustrated in
Herein, the wiretapping period determining unit 1101 determines the wiretapping period T as the sum of the error rate measurement period T1, the wiretapping determination operation period T2, the wiretapping notification period T3, and the wiretapping countering period T4. However, alternatively, since the wiretapping determination operation period T2 and the wiretapping countering period T4 are sufficiently smaller periods of time as compared to the error rate measurement period T1 and the wiretapping notification period T3, the wiretapping period determining unit 1101 determines the wiretapping period T based on the error rate measurement period T1 and the wiretapping notification period T3.
Meanwhile, the wiretapping determination operation period T2, the wiretapping notification period T3, and the wiretapping countering period T4 are assumed to be estimate values. Alternatively, the wiretapping period T can be determined using actually-measured values (actual measurement values). Moreover, the error rate measurement period T1, the wiretapping determination operation period T2, the wiretapping notification period T3, and the wiretapping countering period T4 can be allowed to be input using an input unit (not illustrated). Furthermore, the wiretapping period T (or the wiretapping period T′) can be set in advance as a predetermined value in the wiretapping period determining unit 1101.
As illustrated in
Moreover, if wiretapping has not occurred before the timing ta, even if the cryptographic key that was used in the wiretapping period T from the timing ta to the timing tf was used before the timing ta too, the wiretapper who started wiretapping after the timing ta does not obtain the data encrypted by the same cryptographic key before the timing ta. Thus, the cryptographic key used in the wiretapping period T from the timing ta to the timing tf is identical to a disposable cryptographic key used only once to the wiretapper. In connection with that, with reference to
As illustrated in
The encrypting unit 105 obtains, from the generating unit 102, a cryptographic key having the size L′ that is greater than the size L of the application data which is output during each wiretapping period T by the data generating unit 104 to the encrypting unit 105. As described earlier, the wiretapping period T is determined by the wiretapping period determining unit 1101, and the size L′ is determined by the determining unit 110. The determining unit 110 sends the information about the size L′ and about the wiretapping period T to the generating unit 102. Then, for example, via the optical data communication channel of the optical fiber link 3, the generating unit 102 sends the information about the size L′ and about the wiretapping period T to the generating unit 202. With that, the decrypting unit 205 can obtain the cryptographic key having the size L′ from the generating unit 202, and can repeatedly use the cryptographic key having the size L′ during each wiretapping period T.
Explained below with reference to
Step S101
As described earlier, the wiretapping period determining unit 1101 of the determining unit 110 adds the error rate measurement period T1 set as a predetermined period of time, the wiretapping determination operation period T2 set as an estimate value, the wiretapping notification period T3 set as an estimate value, and the wiretapping countering period T4 set as an estimate value; and determines (calculates) the wiretapping period T (=T1+T2+T3+T4). Thus, the wiretapping period T represents the period of time from the start of wiretapping by a wiretapper up to the detection of (the possibility) of wiretapping and execution of the wiretapping countering operation. Meanwhile, instead of determining the wiretapping period T, the wiretapping period determining unit 1101 can determine the wiretapping period T′ (=T+α) that is obtained by adding the margin value α to the wiretapping period T. Then, the system control proceeds to Step S102.
Step S102
The generation rate determining unit 1102 of the determining unit 110 determines the generation rate R (bytes/second) at which the data generating unit 104 generates application data per unit of time and sends it to the encrypting unit 105, and determines the generation rate R′ that is greater than the maximum value of the generation rate R. The generation rate R′ can be set in advance as a predetermined value in the generation rate determining unit 1102. Alternatively, the generation rate R′ can be an actually-measured value (actual measurement value). Then, the system control proceeds to Step S103.
Step S103
The determining unit 110 multiplies the wiretapping period T, which is determined by the wiretapping period determining unit 1101, and the generation rate R′, which is determined by the generation rate determining unit 1102, and determines (calculates) the size L′ that is greater than the size L of the application data which is output during each wiretapping period T by the data generating unit 104 to the encrypting unit 105. The size L′ can be set in advance as a predetermined value in the determining unit 110.
As a result of performing the operations from Steps S101 to S103, the determining unit 110 determines the size L′ of cryptographic keys. As described earlier, the size L′ of cryptographic keys that is determined by the determining unit 110 is greater than the size L of the application data to be encrypted. Hence, encryption of the application data using a cryptographic key having the size L′ implies encryption according to a total encryption method that makes it impossible to decipher the application data.
Explained below with reference to
Step S111
The encrypting unit 105 starts a timer for measuring the elapse of the wiretapping period T and sets a pointer indicating the start portion for use at the initial position of the cryptographic key K1 (at the leading position of the cryptographic key K1) as illustrating in (a) in
Step S112
The encrypting unit 105 determines whether or not the timer has run beyond the wiretapping period T. If the timer has run beyond the wiretapping period T (Yes at Step S112), then the system control returns to Step S111. However, if the timer has not run beyond the wiretapping period T (No at Step S112), then the system control proceeds to Step S113.
Step S113
The encrypting unit 105 determines whether or not an encryption termination instruction (described later) is received as a wiretapping countering operation from the wiretapping countering unit 109. When the encryption termination instruction is received (Yes at Step S113), the repetitive usage of the cryptographic key is ended. However, if the encryption termination instruction is not received (No at Step S113), the system control proceeds to Step S114.
Step S114
The encrypting unit 105 determines whether or not the application data to be transmitted to the node 2 (transmission data illustrated in (b) in
Step S115
The encrypting unit 105 deducts the size L of the application data, which is received from the data transmitting unit 106, from the remaining cryptographic key size, and sets the resultant size as the remaining cryptographic key size for the new cryptographic key K1. Then, the system control proceeds to Step S116.
Step S116
The encrypting unit 105 determines whether or not the remaining cryptographic key size is equal to or greater than “0”. If the remaining cryptographic key size is equal to or greater than “0” (Yes at Step S116), the system control proceeds to Step S117. However, if the remaining cryptographic key size is not equal to or greater than “0” (No at Step S116), that is, if there is no remaining portion of the cryptographic key K1 that can be used in encrypting the application data, then the operation for repetitive usage of a cryptographic key is ended.
Step S117
The encrypting unit 105 obtains, from the obtained cryptographic key K1, a cryptographic key having the size L, which is the size of the application data (the transmission data), from the current position of the pointer. Then, as illustrated in (c) in
Step S118
The encrypting unit 105 encrypts the application data, which has the size L, using the cryptographic key having the size L and obtained from the cryptographic key K1; and transmits the cryptographic data to the node 2 via the data transmitting unit 106.
As illustrated in
Returning to the explanation with reference to
In
As described above, until the wiretapping detecting unit 207 detects the possibility of wiretapping and the wiretapping countering unit 109 performs the wiretapping countering operation, the encrypting unit 105 performs encryption by repeatedly using the same cryptographic key (in the example illustrated in
For example, if the generation rate for generating application data in the data generating unit 104 of the node 1 is 10 [megabytes/second], and if the operations are performed for 10 [hours] so that the data to be transmitted is encrypted using different cryptographic keys one after another according to the one-time pad method, then the cryptographic keys worth 360 [gigabytes] are consumed as given below in Equation (1).
10 [megabytes/second]×36000 [seconds] (10 [hours])=360 [gigabytes] (1)
In contrast, as described above, in the case of using the same cryptographic key in a repeated manner during each wiretapping period T until the possibility of wiretapping is detected, if the wiretapping period T is set to be equal to 1 [minute] and if the generation rate for generating application data in the data generating unit 104 is 10 [megabytes/second]; when there is no wiretapping during the 10 [hours] of continuous operations, cryptographic keys worth only 0.6 [gigabytes] are consumed as given below in Equation (2).
10 [megabytes/second]×60 [seconds](1 [minute])=0.6 [gigabytes] (2)
In the example illustrated in
More particularly, after the wiretapping recognizing unit 107 recognizes the possibility of wiretapping, the wiretapping countering unit 109 receives an instruction to perform the wiretapping countering operation from the wiretapping recognizing unit 107 and sends an encryption termination instruction to the encrypting unit 105. Upon receiving the encryption termination instruction from the wiretapping countering unit 109, the encrypting unit 105 terminates the use of the cryptographic key K1 that was used during each wiretapping period T. Then, the encrypting unit 105 receives application data from the data generating unit 104; obtains another cryptographic key different from the cryptographic key K1; and performs encryption according to the one-time pad method. The data transmitting unit 106 then transmits the cryptographic data. That is, after terminating the use of the cryptographic key K1, the encrypting unit 105 uses different cryptographic keys one after another and encrypts each piece of application data according to the one-time pad method. In this way, in the case of performing encryption according to the one-time pad method, it becomes necessary to have the cryptographic keys equivalent to the same size as the size of the application data.
As a result of performing the wiretapping countering operation illustrated in
In the example illustrated in
More specifically, after the wiretapping recognizing unit 107 recognizes the possibility of wiretapping, the wiretapping countering unit 109 receives an instruction to perform the wiretapping countering operation from the wiretapping recognizing unit 107 and sends an encryption termination instruction to the encrypting unit 105. Upon receiving the encryption termination instruction from the wiretapping countering unit 109, the encrypting unit 105 terminates the use of the cryptographic key K1 that was repeatedly used for each wiretapping period T. As a result of terminating the use of the cryptographic key K1 by the encrypting unit 105, the data transmission operation performed by the data transmitting unit 106 is also stopped.
Subsequently, when it is detected that the possibility of wiretapping no longer exists, the wiretapping detecting unit 207 sends a wiretapping end signal to the wiretapping notification transmitting unit 208. Upon receiving the wiretapping end signal from the wiretapping detecting unit 207, the wiretapping notification transmitting unit 208 transmits a wiretapping end notification signal to the wiretapping notification receiving unit 108 of the node 1 via the classical communication channel (such as the optical data communication channel). That is, as a result of transmitting a wiretapping end notification signal to the node 1, the wiretapping notification transmitting unit 208 notifies the node 1 about the fact that the possibility of wiretapping with respect to the data in the optical data communication channel no longer exists. Upon receiving the wiretapping completion notification signal from the wiretapping notification transmitting unit 208, the wiretapping notification receiving unit 108 sends a wiretapping end signal to the wiretapping recognizing unit 107. As a result of receiving the wiretapping end signal from the wiretapping notification receiving unit 108, the wiretapping recognizing unit 107 recognizes that the possibility of wiretapping with respect to the optical data communication channel no longer exists. Upon recognizing that the possibility of wiretapping no longer exists, the wiretapping recognizing unit 107 instructs the wiretapping countering unit 109 that the wiretapping countering operation is no longer required. Upon receiving the instruction from the wiretapping recognizing unit 107 that the wiretapping countering operation is no longer required, the wiretapping countering unit 109 stops performing the wiretapping countering operation, and sends an encryption resumption instruction to the encrypting unit 105.
The encrypting unit 105 obtains the cryptographic key K2 (a second cryptographic key), which has the size L′ but which is different from the cryptographic key K1. Then, the encrypting unit 105 encrypts the application data by repeatedly using the cryptographic key K2 during each wiretapping period T, and transmits cryptographic data to the node 2 via the data transmitting unit 106. Meanwhile, since the decrypting unit 205 has already obtained the information about the size L′ from the encrypting unit 105, the decrypting unit 205 obtains the cryptographic key K2 (the cryptographic key shared with the node 1), which has the size L′ but which is different from the cryptographic key K1. Then, the decrypting unit 205 decrypts the received cryptographic data by repeatedly using the cryptographic key K2 during each wiretapping period T.
In the example illustrated in
In the example illustrated in
In the example illustrated in
For example, as explained in the first embodiment, until the possibility of wiretapping is detected, the same cryptographic key K1 is repeatedly used in each wiretapping period T (set to 1 [minute]). When the possibility of wiretapping is detected, encryption is performed by switching to the conventional one-time pad method. Consider a case in which, since the detection of the possibility of wiretapping, it takes 3 [hours] to detect the fact that the possibility of wiretapping no longer exists; and in which the cryptographic key K2 that is different from the cryptographic key K2 is used again in a repeated manner during each wiretapping period T. Moreover, it is assumed that the generation rate for generating application data in the data generating unit 104 of the node 1 is 10 [megabytes/second], and that the operations are performed for 10 [hours] in all. In this case, as compared to the amount of consumption of 360 [gigabytes] of cryptographic keys as given earlier in Equation (1), cryptographic keys worth only 109.2 [gigabytes] are consumed as given below in Equation (3).
0.6 [gigabytes]+10 [megabytes/second]×10800 [seconds](3 [hours])+0.6 [gigabytes]=109.2 [gigabytes] (3)
Regarding a first modification example, the explanation is given with the focus on the differences with the communication system 100 according to the first embodiment. In the first embodiment, the node 1 functioning as a transmitter includes a data transmitting unit (in
As illustrated in
The generating unit 102a is a functional unit that receives information about the length (the size L′) of the cryptographic key via the optical data communication channel from a generating unit 202a and that generates a cryptographic key for the purpose of encrypting the data received by the data receiving unit 106a by obtaining a cryptographic key having the size L′ from the storing unit 103. The generating unit 102a includes the key distilling unit 1021, which has identical functions to the key distilling unit 1021 illustrated in
The data using unit 104a is an application running in the node 1a for handling a variety of data and is a functional unit that receives application data that was received by the decrypting unit 105a from the node 2a, and makes use of the application data.
The decrypting unit 105a is, as described later, a functional unit that receives cryptographic data from the data receiving unit 106a, that obtains the cryptographic key from the generating unit 102a, and that decrypts the cryptographic data using the cryptographic key. Moreover, the decrypting unit 105a sends application data, which is obtained by decrypting the cryptographic data, to the data using unit 104a.
The data receiving unit 106a is a functional unit that converts optical signals, which are received from a data transmitting unit 206a via the optical data communication channel, into cryptographic data and that sends it to the decrypting unit 105a. The data receiving unit 106a is implemented by the optical processing device 85 illustrated in
As illustrated in
The generating unit 202a is a functional unit that generates a cryptographic key, which is to be used in encrypting the data transmitted from the data transmitting unit 206a, by obtaining a cryptographic key, which has the length (the size L′) determined by the determining unit 210 (described later), from the storing unit 203. Moreover, the generating unit 202a transmits the information about the size L′, which represents the length of cryptographic keys as determined by the determining unit 210, to the generating unit 102a via the optical data communication channel. The generating unit 202a includes the key distilling unit 2021 (a key distilling unit), which has identical functions to the functions of the key distilling unit 2021 of the node 2 illustrated in
The data generating unit 204a is an application running in the node 2a for handling a variety of data and is a function unit that sends application data, which is to be sent to the node 1a, to the encrypting unit 205a.
The encrypting unit 205a is a functional unit that receives application data from the data generating unit 204a, that obtains the cryptographic key from the generating unit 202a, and that encrypts the application data using the cryptographic key. Then, the encrypting unit 205a sends the encrypted application data (cryptographic data) to the data transmitting unit 206a.
The data transmitting unit 206a is a functional unit that converts the cryptographic data, which is received from the encrypting unit 205a, into optical signals and that transmits the optical signals of the cryptographic data to the data receiving unit 106a of the node 1 via the optical data communication channel of the optical fiber link 3. The data transmitting unit 206a is implemented by the optical processing device 85 illustrated in
The wiretapping detecting unit 207 is a functional unit that obtains the error rate of the photon communication channel (the quantum communication channel) as calculated during the key distillation operation performed by the key distilling unit 2021 of the generating unit 202a, that performs the wiretapping determination operation based on the error rate, and that detects the possibility of wiretapping by a wiretapper. For example, when the obtained error rate is greater than a predetermined threshold value, the wiretapping detecting unit 207 detects that there is a possibility of wiretapping. When the possibility of wiretapping is detected, the wiretapping detecting unit 207 sends a wiretapping detection signal to the wiretapping countering unit 209. Thus, herein, the data (such as application data) communicated using the optical data communication channel is the target for wiretapping intended by the wiretapper; and the possibility of wiretapping with respect to the data in the optical data communication channel is detected based on the error rate of the photon string in the optical photon communication channel that is formed in the same optical fiber link 3 as a result of implementing the coexistence technology.
The wiretapping countering unit 209 is a functional unit that receives an instruction to perform the wiretapping countering operation from the wiretapping detecting unit 207 and that performs the wiretapping countering operation.
The determining unit 210 is a functional unit that determines the size L′ that is greater than the size L of the application data sent by the data generating unit 204a to the encrypting unit 205 during the wiretapping period T that includes the time slot within which the data is at risk of being actually wiretapped in the optical data communication channel. Herein, the method of determining the size L′ is identical to the first embodiment. Meanwhile, the determining unit 210 includes a wiretapping period determining unit 2101 (a first determining unit) and a generation rate determining unit 2102.
The wiretapping period determining unit 2101 is a functional unit that determines the wiretapping period T that includes the time slot within which the data that is at risk of being actually wiretapped is transmitted using the optical data communication channel. The method of determining the wiretapping period T is identical to the first embodiment except for the fact that the wiretapping communication period T3 need not be taken into account.
The generation rate determining unit 2102 is a functional unit that determines the generation rate R′ that is greater than the maximum value of the generation rate R at which the data generating unit 204a generates application data per unit of time and sends it to the encrypting unit 205a. The method of generating the generation rate R′ is identical to the first embodiment.
Given below is the explanation of the operation for repetitive usage of a cryptographic key in the communication system 100a and the wiretapping countering operation in the case of detection of the possibility of wiretapping in the communication system 100a.
In an identical manner to the operations illustrated in
The encrypting unit 205a obtains, from the generating unit 202a, a cryptographic key having the size L′ that is greater than the size L of the application data which is output during each wiretapping period T by the data generating unit 204a to the encrypting unit 205a. As described earlier, the wiretapping period T is determined by the wiretapping period determining unit 2101 of the determining unit 210, and the size L′ is determined by the determining unit 210. The determining unit 210 sends the information about the size L′ and the wiretapping period T to the generating unit 202a. Then, for example, via the optical data communication channel of the optical fiber link 3 (a physical medium), the generating unit 202a transmits the information about the size L′ and the wiretapping period T to the generating unit 102a. With that, the decrypting unit 105a can obtain the cryptographic key having the size L′ from the generating unit 102a, and can repeatedly use the cryptographic key having the size L′ during each wiretapping period T.
The wiretapping countering operation includes terminating the use of the cryptographic key K1 that was repeatedly used during each wiretapping period T till the timing tf (see
In this way, even in a configuration in which the node 1a functioning as a transmitter includes a data receiving unit and the node 2a functioning as a receiver includes a data transmitting unit, the effect is identical to the effect achieved in the first embodiment. That is, in the first modification example, until the wiretapping detecting unit 207 detects the possibility of wiretapping and the wiretapping countering unit 209 performs the wiretapping countering operation, the encrypting unit 205a performs encryption by repeatedly using the same cryptographic key (in the example illustrated in
Meanwhile, the other encryption-related operations explained with reference to
Moreover, the configuration can alternatively be such that the node 1a functioning as a transmitter as well as the node 2a functioning as a receiver includes a data transmitting unit and a data receiving unit. In that case, it is desirable that the cryptographic key used in encrypting the data to be transmitted from the node 1a (i.e., the cryptographic key used in decrypting the data received by the node 2a) is different from the cryptographic key used in encrypting the data to be transmitted from the node 2a (i.e., the cryptographic key used in decrypting the data received by the node 1a). As a result, in case a wiretapper performs wiretapping with respect to the optical data communication channel, it becomes possible to avoid a situation in which a plurality of pieces of application data encrypted using the same cryptographic key is wiretapped.
Regarding a second modification example, the explanation is given with the focus on the differences with the communication system 100 according to the first embodiment. Herein, the communication system according to the second modification example is assumed to have an identical configuration to the configuration of the communication system 100 illustrated in
As illustrated in
When the wiretapping recognizing unit 107 recognizes the possibility of wiretapping, the wiretapping countering unit 109 receives an instruction for performing the wiretapping countering operation from the wiretapping recognizing unit 107 and sends an encryption termination instruction to the encrypting unit 105. Upon receiving the encryption termination instruction from the wiretapping countering unit 109, the encrypting unit 105 terminates the use of the cryptographic keys K1a and K1b that were being repeatedly used during each wiretapping period T. As a result of terminating the use of the cryptographic keys K1a and K1b by the encrypting unit 105, the data transmission operation performed by the data transmitting unit 106 is also stopped.
As a result of performing such operations, it becomes possible to achieve an identical effect to the effect achieved in the first embodiment.
Regarding a communication system according to a second embodiment, the explanation is given with the focus on the differences with the communication system 100 according to the first embodiment. In the first embodiment, the possibility of wiretapping of data in the classical communication channel (the optical data communication channel) is detected based on the error rate of the photon communication channel formed in the optical fiber link 3. In contrast, in the second embodiment, the explanation is given for an operation for detecting the possibility of wiretapping by capturing a monitoring area using an imaging device.
As illustrated in
The node 1b is a transmitter that transmits, to the node 2b via the quantum communication channel 3a, a photon string that is made of laser-generated single photons which serve as the basis for generating cryptographic keys. In the example illustrated in
The node 2b is a receiver that receives, from the node 1b via the quantum communication channel 3a, the photon string made of single photons that serve as the basis for generating cryptographic keys. In the example illustrated in
The quantum communication channel 3a is an optical fiber used in sending and receiving photons. The classical communication channel 3b is a communication channel used in sending and receiving the control information and the application data. Herein, the classical communication channel 3b is implemented using a communication cable such as an optical fiber or an Ethernet (registered trademark) cable that enables sending and receiving normal digital data.
The imaging device 4 is a camera device that captures the condition of a monitoring area 5. The imaging device 4 is communicably connected to the node 1b either in a wired manner or in a wireless manner. The data captured by the imaging device 4 can be in the form of still images or moving images taken at predetermined intervals. In the following explanation, the data captured by the imaging device 4 is sometimes simply called “image information” (a detection result). As illustrated in
The single photons output by the node 1b are transmitted to the node 2b via the quantum communication channel 3a. The communication data such as the control information and the application data is communicated between the nodes 1b and 2b via the classical communication channel 3b.
Meanwhile, in the communication system 100b, during the key distillation operation that is required for the purpose of sharing cryptographic keys between the nodes 1b and 2b, the necessary control information either can be exchanged using the classical communication channel 3b as described above or can be exchanged using a separate dedicated channel formed in the quantum communication channel 3a, which is an optical fiber for sending and receiving photons, by implementing the WDM technology.
Meanwhile, the data communicated using the classical communication channel 3b can be any type of data. As described earlier, the control information required in the key distillation operation and the application data can be exchanged or some other general-purpose data can be exchanged using the classical communication channel 3b.
As illustrated in
The wiretapping detecting unit 107b performs image analysis with respect to the image information captured by the imaging device 4, and detects a person or an object that may wiretap the data in the classical communication channel 3b within the monitoring area 5. Thus, when a person or an object that may perform wiretapping is detected as a result of performing image analysis with respect to the image information, the wiretapping detecting unit 107b detects the possibility of wiretapping. When the possibility of wiretapping is detected, the wiretapping detecting unit 107b instructs the wiretapping countering unit 109 to perform a wiretapping countering operation.
The wiretapping countering unit 109 is a functional unit that performs, upon receiving the instruction to perform the wiretapping countering operation from the wiretapping detecting unit 107b, the wiretapping countering operation. The specific contents of the wiretapping countering operation are identical to the first embodiment.
The determining unit 110 is a functional unit that determines the size L′ that is greater than the size L of the application data sent by the data generating unit 104 to the encrypting unit 105 during the wiretapping period T that includes the time slot within which the data that is at risk of being actually wiretapped is transmitted using the classical communication channel 3b. The method of determining the size L′ is identical to the first embodiment. The determining unit 110 includes the wiretapping period determining unit 1101 (a first determining unit) and the generation rate determining unit 1102.
The wiretapping period determining unit 1101 is a functional unit that determines the wiretapping period T that includes the time slot within which the data is at risk of actually being wiretapped in the classical communication channel 3b. Regarding the method of determining the wiretapping period T, the explanation is given later.
The generation rate determining unit 1102 is a functional unit that determines the generation rate R′ greater than the maximum value of the generation rate R at which the data generating unit 104 generates application data per unit of time and sends it to the encrypting unit 105. The method of generating the generation rate R′ is identical to the first embodiment.
As illustrated in
As illustrated in
When the possibility of wiretapping is detected, the wiretapping detecting unit 107b instructs the wiretapping countering unit 109 to perform a wiretapping countering operation. Upon receiving the instruction to perform a wiretapping countering operation from the wiretapping detecting unit 107b, the wiretapping countering unit 109 performs the wiretapping countering operation. As illustrated in
The wiretapping period determining unit 1101 of the determining unit 110 determines, as the wiretapping period T, a period of time equal to or greater than the period of time between the timings tb2 and tf2. In that case, the period of time between the timings tb2 and tf2 varies according to the quality of the imaging device 4, or the image processing capacity, or the communication quality between the imaging device 4 and the wiretapping detecting unit 107b. For that reason, although the period of time from the timing tb2 to the timing tf2 varies in reality, the worst-case value can be set as the wiretapping period T. Of the wiretapping period T, since the timing at which the wiretapping is actually started comes after the timing tb2, the period of time in which the data is at risk of being actually wiretapped is included in the wiretapping period T. Meanwhile, in an identical manner to the first embodiment, instead of determining the wiretapping period T, the wiretapping period determining unit 1101 can determine the wiretapping period T′ (=T+α) obtained by adding the margin value α in the wiretapping period T.
Alternatively, the wiretapping period T can be determined using actually-measured values (actual measurement values). Still alternatively, the wiretapping period T can be allowed to be input using an input unit (not illustrated). Still alternatively, the wiretapping period T (or the wiretapping period T′) can be set in advance as a predetermined value in the wiretapping period determining unit 1101.
As illustrated in
Moreover, if wiretapping has not occurred before the timing tb2, even if the cryptographic key that is used in the wiretapping period T from the timing tb2 to the timing tf2 was used before the timing tb2 too, the wiretapper who started wiretapping after the timing tb2 does not obtain the data encrypted by the same cryptographic key before the timing tb2. Thus, the cryptographic key used in the wiretapping period T from the timing tb2 to the timing tf2 is identical to a disposable cryptographic key used only once to the wiretapper.
Meanwhile, the operation for repetitive usage of a cryptographic key as performed in the communication system 100b according to the second embodiment is identical to the operation performed in the communication system 100 according to the first embodiment.
Given below is the explanation of the wiretapping countering operation according to the second embodiment. In
In this way, the wiretapping detecting unit 107b performs image analysis with respect to the image information captured by the imaging device 4, and detects the possibility of wiretapping. Until the wiretapping countering unit 109 performs the wiretapping countering operation, the encrypting unit 105 performs encryption using the same cryptographic key in a repeated manner during each wiretapping period T. When the wiretapping detecting unit 107b detects the possibility of wiretapping, the wiretapping countering unit 109 performs the wiretapping countering operation that includes making the encrypting unit 105 to terminate the use of the cryptographic key that was repeatedly used during each wiretapping period T and making the data transmitting unit 106 to stop the data transmission operation. As a result, as compared to the case in which the data to be transmitted is encrypted using different cryptographic keys one after another according to the conventional one-time pad method; the amount of consumption of the cryptographic keys, which are shared between and stored in the nodes 1b and 2b, can be reduced to a large extent.
Meanwhile, the other encryption-related operations explained with reference to
The encrypting unit 105 obtains the cryptographic key K2, which has the size L′ but which is different from the cryptographic key K1, from the generating unit 102. Then, the encrypting unit 105 encrypts the application data by repeatedly using the cryptographic key K2 during each wiretapping period T, and transmits cryptographic data to the node 2 via the data transmitting unit 106. Meanwhile, since the decrypting unit 205 has already obtained the information about the size L′ from the encrypting unit 105, the decrypting unit 205 obtains the cryptographic key K2 (the cryptographic key shared with the node 1), which has the size L′ but which is different from the cryptographic key K1. Then, the decrypting unit 205 decrypts the received cryptographic data by repeatedly using the cryptographic key K2 during each wiretapping period T.
Meanwhile, in the second embodiment, although the imaging device 4 is assumed to be a camera device, that is not the only possible case. Alternatively, for example, the imaging device 4 can be a sensor device such as a human sensor.
Regarding a first modification example, the explanation is given with the focus on the differences with the communication system 100b according to the second embodiment. In the second embodiment, the imaging device 4 is connected to the node 1b functioning as a transmitter. In contrast, in the first modification example, the explanation is given for a configuration in which the imaging device 4 is connected to the node 2b functioning as a receiver.
As illustrated in
The determining unit 110 is a functional unit that determines the size L′ that is greater than the size L of the application data sent by the data generating unit 104 to the encrypting unit 105 during the wiretapping period T that includes the time slot within which the data that is at risk of being actually wiretapped is transmitted using the classical communication channel 3b. The method of determining the size L′ is identical to the first embodiment. The determining unit 110 includes the wiretapping period determining unit 1101 (a first determining unit) and the generation rate determining unit 1102.
The wiretapping period determining unit 1101 is a functional unit that determines the wiretapping period T that includes the time slot within which the data is at risk of actually being wiretapped in the classical communication channel 3b. The method of determining the wiretapping period T is identical to the second embodiment.
The generation rate determining unit 1102 is a functional unit that determines the generation rate R′ that is greater than the maximum value of the generation rate R at which the data generating unit 104 generates application data per unit of time and sends it to the encrypting unit 105. The method of generating the generation rate R′ is identical to the first embodiment.
As illustrated in
The wiretapping detecting unit 207c performs image analysis with respect to the image information captured by the imaging device 4 (a detecting unit), and detects a person or an object that may wiretap the data in the classical communication channel 3b within the monitoring area 5. Thus, when a person or an object that may perform wiretapping is detected as a result of performing image analysis with respect to the image information, the wiretapping detecting unit 207c detects the possibility of wiretapping. When the possibility of wiretapping is detected, the wiretapping detecting unit 207c sends a wiretapping detection signal to the wiretapping notification transmitting unit 208.
The imaging device 4 is a camera device that captures the condition of the monitoring area 5. The imaging device 4 is communicably connected to the node 2c (the wiretapping detecting unit 207c) either in a wired manner or in a wireless manner to be able to communicate data.
With such a configuration, even when the imaging device 4 is connected to the node 2, it becomes possible to achieve the same effect as the effect achieved in the second embodiment.
Regarding a second modification example, the explanation is given with the focus on the differences with the communication system 100b according to the second embodiment. The communication system 100b according to the second embodiment includes functional units for sending and receiving photons between the nodes and for generating and sharing cryptographic keys by performing the key distillation operation. In contrast, in the second modification example, the explanation is given for a case in which a large number of common cryptographic keys are stored in advance in the storing units 103 and 203, and the operation for sending and receiving photons as well as the key distillation operation are not performed.
As illustrated in
The generating unit 102d is a functional unit that generates a cryptographic key for the purpose of encrypting the data transmitted from the data transmitting unit 106, by obtaining a cryptographic key having the length (the size L′) determined by the determining unit 110. Moreover, the generating unit 102d transmits information about the size L′, which represents the length of cryptographic keys as determined by the determining unit 110, to a generating unit 202d via the optical data communication channel. Meanwhile, in the second modification example, the generating unit 102d does not include the key distilling unit 1021 for performing the key distillation operation illustrated in
As illustrated in
The generating unit 202d is a functional unit that receives information about the length (the size L′) of cryptographic keys via the optical data communication channel from the generating unit 102d and that generates a cryptographic key, which is to be used in decrypting the data received by the data receiving unit 206, by obtaining a cryptographic key having the size L′ (a first cryptographic key) from the storing unit 203. In the second modification example, the generating unit 202d does not include the key distilling unit 2021 for performing the key distilling operation illustrated in
In this way, even if the operation for sending and receiving photons is not performed and new cryptographic keys are not generated by performing the key distilling operation, the cryptographic keys stored in the storing units 103 and 203 can be used to perform the encryption operation (or the decryption operation) in the same way as the communication system 100b according to the second embodiment. Moreover, as compared to a case in which the data to be transmitted is encrypted using different cryptographic keys one after another according to the conventional one-time pad method; the amount of consumption of the cryptographic keys, which are shared between and stored in the nodes 1d and 2d, can be reduced to a large extent.
Meanwhile, in the embodiments and the modification examples described above, the explanation is given for a case in which the cryptographic keys that are originally used in the one-time pad method are generated and used. However, that is not the only possible case. That is, there can be another manner of operation different from using the cryptographic keys as the one-time pad method. For example, the advanced encryption standard (AES) can be used as the encryption method. In that case, during the period of time in which there is no possibility of wiretapping, AES cryptographic keys are used in a repeated manner. However, during the period of time in which there is a possibility of wiretapping, the frequency of updating the AES cryptographic keys can be increased. That is, during the period of time in which there is no possibility of wiretapping, the cryptographic keys are used in a repeated manner. However, during the period of time in which there is a possibility of wiretapping, the intensity of encryption can be enhanced.
Meanwhile, the computer programs executed in the nodes (the communication devices) according to the embodiments and the modification examples described above can be stored in advance in, for example, the ROM 81.
Alternatively, the computer programs executed in the nodes according to the embodiments and the modification examples described above can be recorded as installable or executable files in a computer-readable recording medium such as a compact disk read only memory (CD-ROM), a flexible disk (FD), a compact disk recordable (CD-R), or a digital versatile disk (DVD); and can be provided as a computer program product.
Still alternatively, the computer programs executed in the nodes according to the embodiments and the modification examples described above can be saved as downloadable files on a computer connected to the Internet or can be made available for distribution through a network such as the Internet.
Meanwhile, the computer programs executed in the nodes according to the embodiments and the modification examples described above can make a computer function as the functional units of a node. In such a computer, the CPU 80 can read the computer programs from a computer-readable memory medium, load them in a main memory device, and execute them.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-123024 | Jun 2015 | JP | national |
